mode.js

export default async (req) => {
  const headers = {
    'Content-Type': 'text/css',
    'Netlify-Vary': 'cookie=scheme',
    'Vary': 'Cookie',
    // max-age in seconds = cache for 1 hour
    'Netlify-CDN-Cache-Control': 'public, max-age=3600, stale-while-revalidate=120',
    'Cache-Control': 'public, max-age=360'
  };
  if (req.method === 'GET') {
    const cookie = req.headers.get('Cookie');
    if (cookie?.includes('colorscheme=light')) {
      return new Response(`:root { color-scheme: light; }`, { headers });
    }
    if (cookie?.includes('colorscheme=dark')) {
      return new Response(`:root { color-scheme: dark; }`, { headers });
    }
    
    return new Response(`:root { color-scheme: light dark; }`, { headers });
  }

  if (req.method === 'POST') {
    const b = await req.formData();
    const scheme = b.get('scheme');
    const back = `<meta http-equiv="refresh" content="0; url=${req.headers.get('Referer') || 'https://macwright.com/'}">`
    if (scheme === 'light' || scheme === 'dark') {
      return new Response(back, {
        headers: {
          'Content-Type': 'text/html',
          'Set-Cookie': `colorscheme=${scheme}; SameSite=Lax;`
        }
      })
    } else {
      return new Response(back, {
        headers: {
          'Content-Type': 'text/html',
          'Set-Cookie': 'colorscheme=deleted; Expires=Thu, 01 Jan 1970 00:00:00 GMT'
        }
      })
    }
  }
  return new Response('Method not supported');
}

export const config = { path: "/mode.css" };